it's possible that the game has a different decryption key than the len'en games.
using the key B496F9E992CDB2D2A31A40BE does work with the len'en games but not with this one, and i'm not able to find that anyone did figure out which key the game does use.
the dxlib source code is public so it might be possible to figure out an efficient way to bruteforce a key, though i don't believe anyone's attempted this yet (especially with the new, more secure format).